Frequency dependent core shifts and parameter estimation for the blazar 3C 454.3

We study the core shift effect in the parsec scale jet of the blazar 3C 454.3 using the 4.8 GHz - 36.8 GHz radio light curves obtained from three decades of continuous monitoring. From a piecewise Gaussian fit to each flare, time lags $\Delta t$ between the observation frequencies $\nu$ and spectral indices $\alpha$ based on peak amplitudes $A$ are determined. From the fit $\Delta t \propto \nu^{1/k_r}$, $k_r = 1.10 \pm 0.18$ indicating equipartition between the magnetic field energy density and the particle energy density. From the fit $A \propto \nu^\alpha$, $\alpha$ is in the range $-0.24$ to $1.52$. A mean magnetic field strength at 1 pc, $B_1 = 0.5 \pm 0.2$ G, and at the core, $B_{\rm core} = 46 \pm 16$ mG, are inferred, consistent with previous estimates. The measure of core position offset is $\Omega_{r\nu} = 6.4 \pm 2.8$ pc GHz$^{1/k_r}$ when averaged over all frequency pairs. Based on the statistical trend shown by the measured core radius $r_{\rm core}$ as a function of $\nu$, we infer that the synchrotron opacity model may not be valid for all cases. A Fourier periodogram analysis yields power law slopes in the range $-1.6$ to $-3.5$ describing the power spectral density shape and gives bend timescales in the range $0.52 - 0.66~$yr. This result, and both positive and negative $\alpha$, indicate that the flares originate from multiple shocks in a small region. Important objectives met in our study include: the demonstration of the computational efficiency and statistical basis of the piecewise Gaussian fit; consistency with previously reported results; evidence for the core shift dependence on observation frequency and its utility in jet diagnostics in the region close to the resolving limit of very long baseline interferometry observations.Comment: 12 pages, 11 figures (23 sub-figures), 5 tables. Accepted for publication in MNRA

The core shift effect in the blazar 3C 454.3

Opacity-driven shifts of the apparent VLBI core position with frequency (the "core shift" effect) probe physical conditions in the innermost parts of jets in active galactic nuclei. We present the first detailed investigation of this effect in the brightest gamma-ray blazar 3C454.3 using direct measurements from simultaneous 4.6-43 GHz VLBA observations, and a time lag analysis of 4.8-37 GHz lightcurves from the UMRAO, CrAO, and Metsahovi observations in 2007-2009. The results support the standard Konigl model of jet physics in the VLBI core region. The distance of the core from the jet origin r_c(nu), the core size W(nu), and the lightcurve time lag DT(nu) all depend on the observing frequency nu as r_c(nu)~W(nu)~ DT(nu)~nu^-1/k. The obtained range of k=0.6-0.8 is consistent with the synchrotron self-absorption being the dominating opacity mechanism in the jet. The similar frequency dependence of r_c(nu) and W(nu) suggests that the external pressure gradient does not dictate the jet geometry in the cm-band core region. Assuming equipartition, the magnetic field strength scales with distance r as B = 0.4(r/1pc)^-0.8 G. The total kinetic power of electron/positron jet is about 10^44 ergs/s.Comment: Accepted for publication in MNRAS; 10 pages, 6 figure

Flux density monitoring of extragalactic radio sources. Observations at 22, 37 GHz and 102 MHz within the research programs for the RT-22 CrAO and the Odesa Observatory "URAN-4" IRA NASU

Observations of the millimeter wave emission variability of extragalactic radio sources may give an important information on active processes in their inner parts. The millimeter wave observations of extragalactic radio sources were started with the 22-m radio telescope of the Crimean Astrophysical Observatory in 1973. Since 1973, over 10 000 observations of 140 sources have been obtained. As the extended monitoring programs have demonstrated, there are unpredictable outbursts, quiescent periods, minimum flux levels, and secular trends. As it follows from the analysis, the flare evolution can be divided in three phases: (1) a rapid flux increase; (2) a plateau when the flux relatively constant; (3) a slow intensity decrease. Significant differences in the flare evolution in various optical classes of radio sources were not found. The Odesa Observatory of the Institute of Radio Astronomy of NAS of Ukraine (IRA NASU) have performed a long-term flux monitoring of extragalactic radio sources at 102 MHz with the DKR–1000 radio telescope of the Pushchino Radio Astronomy Observatory of the Astro–Space Center of the Lebedev Physical Institute. About 20 observational sessions of over 80 compact and extended radio sources have been carried out in 1984–1985, 1988–1992, and 1996–1998. The variability of radio sources at meter wavelengths is caused by “scintillations” of the flux density of the inhomogeneity of the local interstellar medium. At the same time, many of sources are showed anomalous flux variations at meter wavelengths that do not correspond to the assumption about interstellar scintillations. In this paper, we present a comparison of the data of two independent observations programs. Own activity of radio sources has been taken into account and the flux variability with the time delay at millimeter and meter wavelengths has been considered. It was possible due to the longer time series of the RT-22 observations

Simeiz VLBI Station - Geodetic and Astrophysical Study

This report gives an overview about the geodetic VLBI activities at the Simeiz station. It also summarizes the seasonal and long-term variability of the Black Sea level near Yalta, Odessa, Ochakov, and Katsively

Optical and Radio Variability of BL Lacertae

We observed the prototype blazar, BL Lacertae, extensively in optical and radio bands during an active phase in the period 2010--2013 when the source showed several prominent outbursts. We searched for possible correlations and time lags between the optical and radio band flux variations using multifrequency data to learn about the mechanisms producing variability. During an active phase of BL Lacertae, we searched for possible correlations and time lags between multifrequency light curves of several optical and radio bands. We tried to estimate any possible variability timescales and inter-band lags in these bands. We performed optical observations in B, V, R and I bands from seven telescopes in Bulgaria, Georgia, Greece and India and obtained radio data at 36.8, 22.2, 14.5, 8 and 4.8 GHz frequencies from three telescopes in Ukraine, Finland and USA. Significant cross-correlations between optical and radio bands are found in our observations with a delay of cm-fluxes with respect to optical ones of ~250 days. The optical and radio light curves do not show any significant timescales of variability. BL Lacertae showed many optical 'mini-flares' on short time-scales. Variations on longer term timescales are mildly chromatic with superposition of many strong optical outbursts. In radio bands, the amplitude of variability is frequency dependent. Flux variations at higher radio frequencies lead the lower frequencies by days or weeks. The optical variations are consistent with being dominated by a geometric scenario where a region of emitting plasma moves along a helical path in a relativistic jet. The frequency dependence of the variability amplitude supports an origin of the observed variations intrinsic to the source.Comment: 10 pages, 9 figures, Accepted for publication in A&

Multi-epoch VLBI of a double maser super burst

In a rare and spectacular display, two well-known massive star forming regions, W49N and G25.65+1.05, recently underwent maser 'super burst' - their fluxes suddenly increasing above 30,000 and 18,000 Jy, respectively, reaching several orders of magnitude above their usual values. In quick-response, ToO observations with the EVN, VLBA and KaVA were obtained constituting a 4 week campaign - producing a high-cadence multi-epoch VLBI investigation of the maser emission. The combination of high-resolution, polarisation and flux monitoring during the burst provides one of the best accounts, to date, of the maser super burst phenomenon, aiding their use as astrophysical tools. These proceedings contain the preliminary results of our campaign

A peculiar multi-wavelength flare in the Blazar 3C 454.3

The blazar 3C454.3 exhibited a strong flare seen in gamma-rays, X-rays, and optical/NIR bands during 3--12 December 2009. Emission in the V and J bands rose more gradually than did the gamma-rays and soft X-rays, though all peaked at nearly the same time. Optical polarization measurements showed dramatic changes during the flare, with a strong anti-correlation between optical flux and degree of polarization (which rose from ~ 3% to ~ 20%) during the declining phase of the flare. The flare was accompanied by large rapid swings in polarization angle of ~ 170 degree. This combination of behaviors appear to be unique. We have cm-band radio data during the same period but they show no correlation with variations at higher frequencies. Such peculiar behavior may be explained using jet models incorporating fully relativistic effects with a dominant source region moving along a helical path or by a shock-in-jet model incorporating three-dimensional radiation transfer if there is a dominant helical magnetic field. We find that spectral energy distributions at different times during the flare can be fit using modified one-zone models where only the magnetic field strength and particle break frequencies and normalizations need change. An optical spectrum taken at nearly the same time provides an estimate for the central black hole mass of ~ 2.3 * 10^9 M_sun. We also consider two weaker flares seen during the $\sim 200$ d span over which multi-band data are available. In one of them, the V and J bands appear to lead the $\gamma$-ray and X-ray bands by a few days; in the other, all variations are simultaneous.Comment: 11 pages, 4 figures, 2 tables; MNRAS in pres

The gravitational radiation power of the blazar OJ 287

Поступила: 15.12.2020. Принята в печать: 30.12.2020.Received: 15.12.2020. Accepted: 30.12.2020.С применением новой модели, основанной на рассмотрении тесных двойных систем (ТДС) из сверхмассивных черных дыр, получены данные для блазара OJ 287, необходимые для нахождения параметров гравитационного излучения OJ 287. Использовались результаты многочастотных мониторингов, выполненных только в радиодиапазоне. Применение гармонических анализов наблюдательных данных позволило построить модель ТДС, состоящих из двух близких по массе сверхмассивных черных дыр (СМЧД), что дало возможность получить найти мощность гравитационного излучения, идущего от OJ 287, вариации орбиты двойной СМЧД и рассмотреть возможность экспериментального определения изменений этих параметров в системе. Рассмотрены варианты излучения электромагнитных и гравитационных волн, идущих от OJ 287 в различных состояниях активности объекта.Using a new model based on the consideration of close binary systems (CDS) of supermassive black holes (SMBHs), we obtained data for the OJ 287 blazar, which is necessary for finding the parameters of the OJ 287 gravitational radiation. We used the results of multi-frequency monitoring performed only in the radio band. The application of harmonic analyses of observational data allowed us to construct a model of CDS consisting of two SMBHs of comparable masses, which made it possible to find the power of gravitational radiation coming from OJ 287, variations in the orbit of the double SMDS, and to consider the possibility of experimentally determining changes in these parameters in the system. Variants of radiation of electromagnetic and gravitational waves coming from OJ 287 in various states of object activity are considered.Исследование выполнено при финансовой поддержке РФФИ в рамках научного проекта 19-29-11027 (Л.Н.В.). В исследовании использованы данные программы мониторинга 40-метрового радиотелескопа OVRO, которая частично поддержана грантами НАСА NNX08AW31G, NNX11A043G, NNX14AQ89G и NSF, а также грантами AST-0808050 и AST-1109911.The research is carried out with the financial support of the RFBR as а part of a scientific project 19-29-11027 (L.N.V.) in the part of the data analysis and the data reduction. The study uses data from the OVRO 40-meter radio telescope monitoring program, which is partially supported by NASA grants NNX08AW31G, NNX11A043G, NNX14AQ89G and NSF, as well as grants AST-0808050 and AST-1109911